Monday, January 07, 2008

The Sunlight to Petrol, or S2P, project essentially reverses the combustion process, recovering the building blocks of hydrocarbons. S2P uses a solar reactor called the Counter-Rotating Ring Receiver Reactor Recuperator, or CR5, to divide carbon dioxide into carbon monoxide and oxygen.

The prototype will be about the size and shape of a beer keg. It will contain 14 cobalt ferrite rings, each about one foot in diameter and turning at one revolution per minute. An 88-square meter solar furnace will blast sunlight into the unit, heating the rings to about 2,600 degrees Fahrenheit. At that temperature, cobalt ferrite releases oxygen. When the rings cool to about 2,000 degrees, they're exposed to CO2.

Since the cobalt ferrite is now missing oxygen, it snatches some from the CO2, leaving behind just carbon monoxide -- a building block for making hydrocarbons -- that can then be used to make methanol or gasoline. And with the cobalt ferrite restored to its original state, the device is ready for another cycle.

Fuels like methanol and gasoline are combinations of hydrogen and carbon that are relatively easy to synthesize, Stechel said. Methanol is the easiest, and that's where they will start, but gasoline could also be made.

Stechel said the Sandia team envisions a day when coal-fired power plants might have large numbers of CR5s, each reclaiming 45 pounds of carbon dioxide using reclamation technology currently under development and producing enough carbon monoxide to make 2.5 gallons of fuel. The Sunlight to Petrol process also raises the possibility that liquid hydrocarbon fuels might one day be renewable – provided CO2 reclamation reaches a point where the greenhouse gas can be snatched directly from the air. Such a process is being explored by Global Research Technologies and Klaus Lakner of Columbia University, among others.

He and Stechel said the technology could be 15 to 20 years from viability on an industrial scale.

This is an intriguing way to make liquid fuels in a renewable way.

If you can get the CO2 directly from the air it is completely renewable. If it uses concentrated CO2 from a coal plant then it can use that CO2 a second time.

I wonder how expensive this will be and how much fuel it can generate per acre? I would like to compare it with biofuels like cellulosic ethanol which also turn sunlight into liquid fuel. It would also be interesting to compare this system and a Prius car with a Tesla battery powered car that uses solar panels to generate its electricity.